IMO "end-to-end encryption" simply isn't possible when the application is run by the same company as the servers the data sits on, is closed source, and can at any time, see the decrypted contents of data it downloads from their servers and do whatever they want with it. Same issue with Proton, MEGA, and any other e2ee app... it's only useful when the company decides not to mess with the data it could always decrypt…
Beyond the privacy marketing angle, e2e allows companies with global exposure to sidestep any unpleasantness when they get a subpoena from Bumfuck, Nowhere. Sure, the NSA, GCHQ and Mossad have a way to exfiltrate the unencrypted data but proprietary e2e is a good thing for most people IMO. Shifts the risk from "my messages are theoretically available to most law enforcement in the globe" to "YOU’RE STILL GONNA BE MOS…
I'm curious as to how well (legally) this "we could modify the app to do it, but nah" approach actually works, and for how long.